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# Re: CRC

- Date: Tue, 13 Feb 1996 06:53:25 PST
- From:
- CC: manta@dartmouth.edu, moo-cows@parc.xerox.com
- In-reply-to: <3120F052.34D9@baymoo.sfsu.edu> (message from Richard Connamacher on Tue, 13 Feb 1996 12:10:58 PST)

    >>>>> "Richard" == Richard Connamacher <phantom@baymoo.sfsu.edu> writes:

        >> Cyclical Redundancy Check, I believe.  It generates a
        >> 'signature' for a chunk of data that can be used to easily
        >> check whether two large chunks of data are the same.

        Richard> Hrm..  how accurate is it?  I would imagine that whever
        Richard> you take a large chunk of data and compress it into a
        Richard> tiny signature, it would be possible for two different
        Richard> sets of data, or more, to have the same signature.  I
        Richard> assume it's much faster than checking if the data itself
        Richard> is identical on both sides of the connection :)

        Richard> Phantom

    It is faster in that the real work is only done once at the origin of
    the data.  It is an information theoretic convolution of the
    inforation, so that a given CRC is capable of detecting N bits in
    error.  For the purpose here, it is unlikeley that to nearly similar
    MOOs would have the same CRC and the same size and the same filedate.
    I would not trust the CRC alone to tell me they were the same -- it is
    more of a flag to say they are different in this case.  If the crc is
    different, the data is most certainly different.  If the crc is the
    same, look at other factors to be sure.

    --
    -----------  "...  And the men went up and viewed Ai."  [Jos 7:2]  -----------
    Robert Jay Brown III  rj@eli.wariat.org  http://eli.wariat.org  1 847 705-0370
    Elijah Laboratories Inc;  759 Independence Drive;  Suite 5;  Palatine IL 60074
    -----  M o d e l i n g   t h e   M e t h o d s   o f   t h e   M i n d  ------

References:

- Re: CRC

- From: Richard Connamacher <phantom@baymoo.sfsu.edu>

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